The present invention relates to packaging for products, such as fresh red meat or other food products, which are enclosed between a support member and a lid, wherein the lid includes a gas-permeable portion and a substantially gas-impermeable portion which is peelably removable from the gas-permeable portion such that the gas-permeable portion remains bonded to the support member, thereby effecting a change in the environmental conditions within the package. More specifically, the invention relates to such packaging wherein individual packages have the gas-impermeable portions thereof peelably removed and are stacked in a retail display case for consumer purchase, thereby creating the possibility that the packaged products in all but the top-most package will become discolored due to oxygen starvation.
Various forms of packaging, particularly for fresh food products such as meat, poultry, and produce, employ a relatively rigid support member, such as a flat sheet or tray, upon or in which a product is supported. A relatively flexible lid or cover is bonded to the support member around the product, generally by forming a heat-seal between the lid and support member, to thereby enclose the product between the lid and support member. This type of packaging is known as "case-ready" packaging because it is generally prepared at a central packaging facility and shipped to a retail outlet in such a form that it is substantially ready to be placed in a retail display case for consumer inspection and purchase without the need for in-store packaging as had traditionally been necessary for fresh foods.
Case-ready packaging encompasses two major varieties: "vacuum" packaging and "modified-atmosphere" packaging. In vacuum, e.g., "vacuum skin" packaging, the lid is thermoformable, i.e., capable of being formed into a desired shape upon the application of heat, and is thermoformed about the product on a support member by means of heat and differential pressure. Virtually all of the air is evacuated from the interior of the package so that the lid conforms very closely to the contour of the packaged product (see, e.g., U.S. Pat. Nos. Re 30,009 (Purdue et al.) and 5,346,735 (Logan et al.), the disclosures of which are hereby incorporated herein by reference). In modified-atmosphere packaging, a food product is generally packaged in a tray-like support member having a peripheral flange to which the lid is secured. Prior to securing the lid to the support member, air is generally evacuated from the interior of the support member and replaced by a gas which extends the shelf-life of the packaged product.
When the packaged product is one which degrades in the presence of oxygen, such as, e.g., beef, poultry, or pork, the product is packaged in a low-oxygen environment and the lid and support member generally provide a substantial barrier to the passage of oxygen therethrough to extend the shelf-life of the packaged product. However, such products may have an unappealing appearance when packaged in a low-oxygen environment. For example, while a low-oxygen packaging environment generally increases the shelf-life of a packaged fresh red meat product (relative to meat products packaged in an environment having a higher oxygen content), red meat has a tendency to assume a purple color when packaged in the absence of oxygen or in an environment having a very low oxygen concentration, i.e., below about 5% oxygen. Such a purple color is undesirable to most consumers, and marketing efforts to teach the consumer about the acceptability of the purple color have been largely ineffective. When meat is exposed to a sufficiently high concentration of oxygen, e.g., as found in air, it assumes a bright red color which most consumers associate with freshness. After 1 to 3 days of such exposure, however, meat assumes a brown color which, like the purple color, is undesirable to most consumers (and indicates that the meat is beginning to spoil). Thus, in order to effectively butcher and package fresh red meat products in a central facility for distribution to retail outlets, the meat is packaged, shipped, and stored in a low-oxygen (vacuum or modified-atmosphere) environment for extended shelf-life, and then displayed for consumer sale in a relatively high-oxygen environment such that the meat is caused to "bloom" into a red color just before being placed in a retail display case. A similar, though not as dramatic, color change occurs with other muscle food products such as poultry and pork.
Blooming of e.g., fresh meat, poultry, or pork products is typically accomplished by constructing the lid of a case-ready package such that it includes a gas-permeable portion and a gas-impermeable portion, with the gas-impermeable portion being peelably removable from the gas-permeable portion in such a manner that the packaged product continues to be enclosed between the gas-permeable portion and support member. Thus, when it is desired to place the package in a retail display case for consumer purchase, the gas-impermeable portion of the lid is peelably removed from the package. Since the remaining portion of the lid is permeable to gas (oxygen), it allows the meat product to bloom in the presence of oxygen which enters the package from the ambient atmosphere. At the same time, the remaining gas-permeable portion of the lid continues to provide protection to the product from, e.g., dirt, dust, moisture, microbial contaminates, etc.
A problem which frequently occurs with case-ready packages, however, is that after the gas-impermeable portion of the lids are removed so that the packaged products bloom, the packages are placed in a retail display case in a stacked configuration, i.e., stacked one on top of the other so that the support member of all but the bottom-most package in the stack is in contact with the remaining gas-permeable lid portion of the package located immediately below. Such stacking arrangement is necessary due to space constraints in retail display cases, and allows the retailer to maximize the number of packages which can be displayed for consumer purchase. Unfortunately, the products packaged in all but the top-most package in the stack often become discolored due to insufficient oxygen flow to such products as a result of intimate contact between the gas-permeable lid portion and the support member of the overlying package in the stack. Since support members in case-ready packages normally consist of gas-impermeable materials, their contact with the gas-permeable lid portion of an underlying package in a stack of packages prevents sufficient oxygen flow through the gas-permeable lid to maintain all or a portion of the underlying packaged product in a state of bloom. The resulting product discoloration is aesthetically unappealing to the consumer, who may assume that the packaged product is defective in some way, e.g., spoiled or beginning to spoil. As can be readily appreciated, this is highly undesirable to the retailer. The problem does not occur to any great extent with traditional retail-packaged cuts of meat because the overwrapping used to enclose the meat product is gathered or folded at the underside of the meat product or a tray used to support the meat product, and allows oxygen to flow into the underlying package in a stack. Accordingly, in order to compete successfully with traditional retail-packaged meat or poultry, case-ready packages must overcome the problem of oxygen starvation of underlying packages in a stack of packages.
One potential solution to this problem is to employ support members having a textured bottom surface so that oxygen can flow between the bottom surface of the support member and into the underlying package in a stack via the gas-permeable lid of the underlying package. While this approach has been successful in many respects, certain drawbacks remain. By definition, a textured surface has a non-smooth or roughened finish with segments (peaks or ridges) that extend from the surface with greater prominence than other segments (valleys). When packages having textured bottom surfaces are placed in a stack, the textured bottoms of all but the lowest package in the stack are forced by gravity against the flexible lids of all but the upper-most package in the stack. The flexible lids of the underlying packages in the stack are, in turn, pressed into the surface of any portion of the packaged products which are in contact with the lids. As a result, both the lids and contacting surface of the products are essentially embossed with the textured pattern of the bottom support member surface of the overlying packages in the stack. The prominent segments of the textured surface produce corresponding indentations in the lid and product surface in the underlying packages. Such indentations in the surface of the packaged products are generally undesirable for aesthetic reasons. Moreover, in the case of fresh meat and poultry products, the indented areas can discolor prematurely due to insufficient oxygen flow thereto, thereby creating a textured pattern of discoloration on the surface of the products in the underlying packages in a stack of such packages.
Another drawback of case-ready packages having a textured bottom surface is that the textured surface does not permit the attachment of a label thereto or direct surface printing thereon bearing desired indicia such as, e.g., product identification or nutritional information. The ability to provide such indicia on the bottom surface of case-ready packages would be a highly desirable feature.
Accordingly, there is a need in the art for case-ready packages which prevent discoloration of packaged products when placed in a stack and which avoid the foregoing shortcomings of case-ready packages having a textured bottom surface.